1. Field of the Invention
This invention relates to a rubber element for tire and a method of manufacturing the same.
2. Description of the Related Art
Among all sorts of elements composing a tire, there is a rubber element for tire comprising a bead core and an apex attached to the bead core. There are conventionally known a rubber element 113 for tire comprising a bead core 101 and an apex 102 whose cross sectional configuration is generally a triangle and attached to the bead core 101 as shown in FIG. 5A, and a rubber element 113 for tire comprising the bead core 101 and an apex (which is called as a bead filler or a stiffener) 103 whose cross sectional configuration is generally a trapezoid and attached to the bead core 101 as shown in FIG. 6.
When forming a tire, a seat-like member 112 comprising layers of an inner and a ply is attached on a former 104 and setting the rubber element 113 for tire on the seat-like member 112, and then the apex 102 is needed to be bent down, i.e. the apex 102 is needed to be made along with the former 104 as shown in FIG. 5B. To bend the apex 102 on its side, the apex 102 is needed to be pressed down with relatively a high pressure by, for example, a stitcher, and this process is bothersome. Moreover because of the pressure applied to the apex (in the processes shown in the FIGS. 5B and 5C), there is a possibility that a joining face 110 between the bead core 101 and the apex 102 is `cracked (separated)`, and air stays in the crack (separation), and a defective tire may be thereby manufactured. Moreover the apex 102 which is once bent down to the former as shown in FIG. 5C may start to rise up (spring up) by elastic restoring force thereof, and a `partial rising` on the sheet-like member 112 is possible to be caused. The apex 103 of the rubber element for tire shown in FIG. 6 is not needed to be bent down to the former in the processes of manufacturing a tire, however an inclined side face 111 of the apex 103 does not fit to the sheet-like member 112 such as a ply, and the apex 103 and the bead core 101 to which the apex 103 is attached slip down from once fixed position on the sheet-like member 112.
To manufacture a rubber element 113 shown in FIG. 6, processes as follows are required. First a sheet-like rubber material 105 is formed as shown in FIG. 7, then cutting the rubber material 105 and forming the apex 103 whose cross sectional configuration is generally a trapezoid, and attaching the apex 103 to the bead core 101. The manufacturing method of such rubber element requires the bothersome operations above, and by manufacturing the rubber element by the conventional method, some parts of the material are left unused and are wasted.
An apex whose sectional configuration is generally a trapezoid is molded by an extrusion machine in some cases, however, a rubber extruded from a die plate of the extrusion machine is twisted and the rubber is not possible to be straighten.
It is therefore an object of the present invention to provide a rubber element for tire which an operation of bending down an apex of the rubber element is not needed when molding a tire, and an inferiority in adhesion of the apex to a sheet-like member is not caused after setting the rubber element for tire, i.e. the rubber element for tire which is possible to increase productivity of tires and to prevent manufacturing defective tires. It is another object of the present invention to provide a simple and sure method of manufacturing the rubber element for tire.